The instant invention deals with a siloxane composition which forms an elastomeric or resinous coating upon cure but when fired to high temperatures at 500.degree. C. or higher, forms a ceramic substance.
Silicone elastomers and resins have been used extensively in the electrical conductive coatings area because of their ability to effectively electrically insulate yet retain excellent physical properties.
These materials are different than the inorganic materials used in past years for this purpose, in that, the inorganic materials when subjected to high temperatures, i.e. 500.degree. C. or higher, would lose their shape and also lose the ability to have the original shape restored. Because of this, coatings would pull away from the conductive substrate and the result would be burning and eventually brittleness of the coating. When this happens, the electrical insulating properties are lost and the wire or cable becomes essentially useless.
Some select siloxane-based electrical insulating materials have been used which hold their original shape but owing to their resinous nature, these materials have little or no flexibility at ordinary temperatures and therefore tend to chip and fall away. These materials can form ceramic-like coatings having excellent heat resistance and electrical properties but their handling properties show limitations leading to drawbacks in processing.
Recently, there has been a high demand for a material which can retain its original shape and electrical insulating ability after exposure to high temperatures, as in the case of fireproof electrical wire, which can be used for bare wiring in emergency electric source circuits. In response to such a demand, new materials were proposed in Japanese publications no. 51 {1976}-60240 and Japanese publication no. 51 {1976}-82319. Since a silica filler is an indispensable component of these materials, the surface portion is burned or partial foaming occurs when the cured product is exposed to high temperatures. Therefore, it is difficult to obtain a ceramic product with a high uniformity and a high dimensional stability. Since a platinum compound is also an indispensable component, the resulting ceramic product is very dense after exposure to high temperatures. Therefore, it is difficult to obtain a low density ceramic with these materials.